Improvements on powertrain NVH are important targets in automotive engineering. This report concentrates on torsional vibration and analyses problem source and vibration system responses. Problems of major concern are discussed in detail. Beside discussions on conventional clutch and damper systems, a new dual mass flywheel concept is introduced: the Hydraulic Torsion Damper (HTD). Functional background and design details are described, showing that controlled slip is an effective way to avoid reversion of disturbing torsional energies and therefore reach torsional isolation without amplification. The slip strategy and the hydraulic control system is introduced along with discussions on oil pump and valve system. From a durability point of view, the question of thermal transport and temperature stability is discussed. Finally, available in-vehicle evaluation results and fatigue test results are shown.